1. Field of the Invention
This invention relates to an improved method for feeding a liquid mixture to the beating cylinder of a production machine for socalled soft ice-cream. The invention also relates to an apparatus for implementing said method.
2. Discussion of the Background
Various types of soft ice-cream production machines are well known to the expert of the art, these being machines for preparing and continuously dispensing portions of soft ice-cream in which the air content is generally around 70%, but can reach as high as 90%. One of these is described and illustrated for example in Italian patent No, 736,656 of Aug. 28 1964.
The machine of that patent comprises an upper mixture feed vessel and a lower beating cylinder connected together by a conduit. The feed vessel is provided with heating and cooling means, by which the mixture is pasteurized before being fed to the beating cylinder.
In machines of this type the entire mixture contained in the feed vessel above the beating cylinder is pasteurized by a traditional process of heating to about +85.degree. C. followed by cooling to about +4.degree. C.
When the machine is fully working, the beating cylinder is fed with pasteurized mixture to be beaten, via controlled communication with the overlying feed vessel, to dispense newly required portions of soft ice-cream.
When the mixture in the feed vessel has reached its bottom level the machine must be halted, and only in this state can a further quantity of mixture fed into the vessel be pasteurized. In this respect, it is impossible to pasteurize the mixture in the feed vessel when the underlying beating cylinder is in operation, this being usable only if red with mixture at a relatively low temperature (around +4.degree. C.), so as not to melt the ice-cream undergoing beating.
Additionally, as is well known to the expert of the art, the mixture can be fed from the vessel to the underlying beating cylinder either by simple gravity fall or with the aid of a pump. Machines of the aforedescribed type suffer from two serious drawbacks.
The first and most important is the problem of hygiene, in that the pasteurized mixture can stagnate for even a considerable time in the feed vessel, which is usually not hermetically sealed but is in communication with the external environment. This favours rapid re-formation of a bacterial load unacceptable in the previously pasteurized mixture.
The second drawback is operational in that, as stated, the feed vessel can only be refilled, and its contained mixture be pasteurized, with the machine at rest.